Monotonic and Cyclic Tests to Determine Short-Term Load

Monotonic and Cyclic Tests to Determine Short-Term Load Duration Performance

of Nail and Bolt Connections

Volume I: Summary Report

Virginia Polytechnic Institute and State University Timber Engineering ReportNo. TE-1994-001

by:

J.D. DolanAssistant Professor of Wood Engineering

S.T. GutshallResearch Assistant

Department of Wood Science and Forest ProductsBrooks Forest Products Center

1650 Ramble RoadBlacksburg, Virginia 24061-0503

and

T.E. McLainDepartment Head and Professor of Wood Engineering

Department of Forest ProductsOregon State University

Corvallis, Oregon 97331-7402

October, 1995

Report No. TE-1994-001 1

SUMMARY

An experimental study of the monotonic and cyclic properties of nailed and bolted woodconnections is described. The objectives of the investigation are 1) determine the effects of cyclicloading on the performance and safety of nail and bolt connections, 2) determine if the value of 1.6used as the load duration factor for wind and seismic design in the 1991 National DesignSpecification for Wood Construction (NDS) is conservative.

Three typical nail and three typical bolt connections were constructed to include three of thefour possible yield modes for wood connections. Two matched samples of each connection type (15specimens for nails and 10 specimens for bolts) were tested monotonically to either catastrophicfailure or a connection slip of 1.0 inches. One matched sample was subjected to cyclic loads priorto being tested monotonically, while the other matched sample represented a control that was testedaccording to methods used to determine design values published in the 1991 NDS. An additionalsample of lumber-to-lumber nail connections were fabricated without pilot holes and tested undermonotonic loading.

Results indicate that prior cyclic loading to magnitudes as high as 2.0 times the nominal designvalues published in the 1991 NDS do not have adverse effects on connection capacity, or ductilityfor nailed and bolted wood connections. This indicates that design seismic events will notsignificantly lower the connection’s ability to resist the loads. Factors-of-safety based on theallowable seismic design values ranged from 1.7 to 3.2 for nail connections, from 2.3 to 4.6 for boltedconnections loaded parallel-to-grain, and from 3.3 to 8.1 for bolted connections loaded perpendicular-to-grain.

High ductilities associated with nail connections and their ability to dissipate large amountsof energy indicate that a factor-of-safety of 1.7 is sufficient to guarantee acceptable performance.The factors-of-safety associated with bolt capacities are sufficient to provide acceptable performanceof wood connections.

Results presented also quantify several cyclic properties such as hysteretic damping, cyclicstiffness, and equivalent viscous damping. Values of these cyclic properties illustrate the ability ofwood connections to dissipate significant quantities of energy during cyclic or dynamic loadingsexpected during natural hazard events such as earthquakes. The ability to dissipate energy improvesa structure’s performance and reliability.

INTRODUCTION

An increase in the load duration factor, C , for wood construction under seismic and windD

loading from 1.33 to 1.6 was included in the 1991 edition of the National Design Specification for®

Wood Construction (NDS ). This change is based on long-term rational that has been applied to®

wood construction. While this increase does not reflect any change in philosophy from previousdesign codes, it highlights an area of limited research support for connections. Lack of research dataraises questions about the load duration increase for seismic loading from historic levels. The basisof the questioning relates to previous connection tests used to determine design values for the NDSwhich were performed with monotonic quasi-static and impact loading, while seismic events producea reversing load effect on the connections.

2 Report No. TE-1994-001

Equations presented in the 1991 NDS for determining allowable design load include twofactors. The first factor adjusts short-term strength to allowable 10-year duration strength. Thisfactor is equal to 1.6 and is based on engineering judgement and results of load duration tests ofwood members. The second factor is a factor-of-safety for the particular yield mode considered. InEquations 8.2-1 to 8.2-6 in the 1991 NDS for bolted connections, constants in the denominator ofeach equation combine the duration-of-load (DOL) and factor-of-safety (FOS). The factor-of-safetyincludes adjustments that account for uncertainty, variability, and calibration to historic performance.Therefore, the constants of each equation can be broken into two components as follows:

!4.0 for MODES I and I becomes 1.6 x 2.5 for DOL and FOS respectivelym s

!3.6 for MODE II becomes 1.6 x 2.25 for DOL and FOS respectively and!3.2 for MODES III , III , and IV becomes 1.6 x 2.0 for DOL and FOS respectively.m s

The change from 1.33 to 1.6 for the DOL factor was made without changing the FOS for all NDSfastener equations. The previous value of 1.33 essentially increased the factor-of-safety for seismicover that used for normal duration loads.

To understand why C = 1.6 is proposed for short-term loads such as seismic actions,D

consider the method used to calculate the nominal design values shown in the 1991 NDS.Connection design values are based on experimental yield loads derived from monotonic tests witha rate of loading causing failure of specimens in 5-10 minutes. This short-term load is then indexedto a nominal design value based on a service duration of 10 years. (Normal or 10-year load durationassumes that wood structures experience a cumulative design load effect of 10 years duration overthe useful life of the structure.) To adjust short-term values to the nominal 10-year loads, values aredivided by 1.6. The 1991 NDS readjusts the nominal values back to a short-term (10-minute) designvalues for seismic loads by multiplying by the load duration factor of 1.6. There are no other factorsimplied in the use of C = 1.6 other than indexing back to short-term design capacity. The 1.6D

load duration factor is conservative since it adjusts the nominal design value to a 10-minute designvalue, whereas an earthquake is a much shorter load event. In fact, if factor-of-safety values remainunchanged, a more accurate load duration factor for seismic design most likely will be higher than1.6 if the capacities continue to be based on monotonic test results.

However, monotonic tests are not representative of cyclic loads such as earthquakes.Monotonic tests do not provide information on any effect of prior cyclic load history on connectioncapacity and/or ductility. There is concern that previous load history may affect connection reservecapacity and/or ductility in situations of cyclic loading.

Long-term static performance information is needed since there currently are no experimentalresults on which to directly base the expected long-term performance of connections. As statedearlier, current procedure for adjusting the short-term experimental results to a 10-year nominal valueare based on long-term material strength tests of wood and engineering judgement. Therefore, whilelong-term connection tests will not address the effect of reversing load such as the cyclic loadingassociated with seismic events, they will provide information that will be useful in correctly settingthe 10-year nominal capacities. This research project was necessary to determine the effects of cyclicload history on nailed and bolted connections and determine effective factors-of-safety for cycliclyloaded connections.


The objectives of this report are as follows:1. Present the results of monotonic tests and load-controlled cyclic tests of nail and

bolt connections.2. Show that short-term cyclic load history on connections, at levels as high as 2.0

times nominal design loads, does not adversely affect on capacity or ductility ofnail and bolt connections.

3. Show that the proposed load duration factor of 1.6 is conservative for laterallyloaded nail and bolt connection in wood if fabricated according to the minimumrequirements of the 1991 NDS.

4. Show that the apparent factors-of-safety for nail and bolt connections, subjectedto prior cyclic loading, provide an acceptable level of performance.

The specific information presented cannot determine directly whether the load duration factorpresented in the 1991 NDS is correct or not since long-term load tests of connections have not beenperformed. The long-term connection tests are required for setting the nominal design values towhich all of the other durations are calibrated.

Detailed and summary information on the connections tests is presented in companion reportsthat are available from the Department of Wood Science and Forest Products, Timber EngineeringCenter, which is located in the Brooks Forest Products Research Center at Virginia PolytechnicInstitute and State University. Detailed data for each specimen tested to determine monotonic andload-controlled cyclic performance tests are presented in Virginia Polytechnic Institute and StateUniversity (VPI) Timber Engineering Report No. TE-1994-002. The summary report and detaileddata for each specimen tested under the Sequential Phased Displacement (SPD) procedure arepresented in VPI Timber Engineering Reports No. TE-1994-003 and No. TE-1994-004 respectively.

TEST PROCEDURES

Specimen ConfigurationsConnection geometries were chosen to represent typical connection details found in

construction in the United States, and to include three of four yield modes that can occur in timberconnections. Connections were in single shear with one dowel fastener. Fifteen specimens of eachnailed connection type and ten specimens of each bolted connection type were tested. Table 1summarizes the types and numbers of replications used for nail connections in monotonic and load-controlled cyclic tests. Table 2 summarizes the same information for bolt connections.

All lumber and plywood used for the tests was purchased at local lumber retailers. Specimenswere constructed from southern pine, and were cut so as to avoid localized defects in the wood asmuch as possible. The wood was conditioned at a temperature of 20 ±3 C and relative humidity of0

65±5% for a minimum of 14 days, or until the equilibrium moisture content was reached. The steelplate used in two connection geometries was also locally purchased and consisted of ¼-inch, ASTMA36 mild carbon steel (ASTM 1989-a) and 18-gauge A446 galvanized sheet steel (ASTM 1989-b).Nails used in two connection geometries were 10 penny (10d) common nails with a diameter of 0.148inches and length of 3 inches. The 16 penny (16d) common nails used in the third nailed connectiongeometry were 0.162 inches in diameter and 3.5 inches long.


Table 1 shows that there were three types of nail connections tested, and each type ofconnection was tested in two configurations for the monotonic test (parallel-to-grain andperpendicular-to-grain) and one configuration for the cyclic test (parallel-to-grain). Twoconfigurations used for monotonic tests were included to investigate effects of grain orientation withrespect to load, while cyclic load history effect was investigated only for the parallel-to-graindirection. Since nailed connections are characterized by yielding of the nails as well as the wood, twoyield modes that represent fastener yielding (modes III and IV) were included. Three types ofs

commonly used connections were included, 1) plywood to lumber which is used in shear walls anddiaphragms, 2) lumber to lumber which is typical of light framing connections, and 3) light-gaugesheet steel to lumber which is typical of joist hangers and other light-gauge metal connectors. Anadditional sample of lumber-to-lumber nail connections without pilot holes was tested to investigatethe effect of pre-drilling pilot holes on nail connection performance. A matched sample of theconnections without pilot holes was also tested under the SPD protocol to investigate the cyclicperformance, with the results being reported in VPI Timber Engineering Reports TE-1994-003 andTE-1994-004. Fifteen replicates were tested in each configuration to provide some information onthe statistical variation in connection performance.

Summary information on type and number of replicates for bolt connection tests is presentedin Table 2. Bolted connections were subjected to monotonic and cyclic loading in the parallel-to-grain orientation and monotonic loading only in the perpendicular-to-grain orientation. Similar to nailconnections, monotonic tests were used with two configurations to investigate effects of grainorientation on the monotonic connection performance, and cyclic load history effects wereinvestigated only for the parallel-to-grain direction.

The stationary member for all bolted connections was defined as the member that wasclamped in a fixed position in the testing fixture, and was located on the nut side of all boltedconnections. For all nailed connections, the stationary member was the penetrated or main memberof the connection. The active member for all connections was defined as the member that was movedby the MTS hydraulic actuator in either a monotonic or cyclic manner during the tests. All boltedconnections tested with the load acting perpendicular-to-grain to the stationary member required thatthe stationary members be wider than the active members in order to meet edge distance requirementsfor the full 1991 NDS design value.

Three types of bolted connection geometries were tested in an effort to include three of fouryield modes possible for bolted connections. Connections were also chosen to simulate typicalconnections used in wood structures. The 2-inch-to-2-inch nominal lumber connection with a ¾-inchbolt represents typical diaphragm chord connections. The 4-inch-to-4-inch nominal lumberconnections with a ¾-inch bolt represents the yield mode expected in a concrete to wood connectionsuch as a ledger board for a roof attached to a tilt-up concrete wall. Finally, the 4-inch nominal-to-¼-inch steel plate connection represents typical connection hardware used in glulam and post-frameconnections.


Table 1: Summary of type and number of nail connection specimens tested under monotonic andload-control cyclic loads.

Fastener Main / Side Expected NumberType Member Load Load Yield of

(inches) Materials Direction Type Mode Replicates

10d Lumber / Parallel- (0.148 x 3.0) 15/32-in Ply to-Grain

Monotonic III 15s

10d Lumber / Perpendicular-(0.148 x 3.0) 15/32-in Ply to-Grain

Monotonic III 15s

10d Lumber / Parallel- Cyclic /(0.148 x 3.0) 15/32-in Ply to-Grain Monotonic

III 15s

16d Lumber /(0.162 x 3.5) Lumber

Parallel-to-Grain Monotonic IV 15

(pilot Holes


Perpendicular-to-Grain Monotonic IV 15

(Pilot Holes)


Parallel-to-Grain Monotonic IV 15(Driven)

16d Lumber / Cyclic /(0.162 x 3.5) Lumber Monotonic

Parallel-to-Grain IV 15

(Pilot Holes)

10d Lumber / Parallel-(0.148 x 3.0) 18-ga. Steel to-Grain

Monotonic III 15s

10d Lumber / Perpendicular-(0.148 x 3.0) 18-ga. Steel to-Grain

Monotonic III 15s

10d Lumber / Parallel- Cyclic /(0.148 x 3.0) 18-ga. Steel to-Grain Monotonic

III 15s


Table 2: Summary of type and number of bolt connection specimens tested under monotonic andload-control cyclic loads.

Fastener Member Load Load Yield ofType Materials Direction Type Mode Replicates

Main / Side Expected Number

3/4-in 2-in / 2-inBolt Nominal Monotonic II 10

Lumber

Parallel-to-Grain

Monotonic II 10

Perpendicular-to-Grain

Parallel- Cyclic /to-Grain Monotonic

II 10

3/4-in Perpendicular-Bolt to-Grain

4-in / 4-inNominal Monotonic III 10Lumber

Parallel-to-Grain

Monotonic IV 10

M


IV 10

1/2-in Steel Plate / Perpendicular-Bolt 4-in Nominal to-Grain

1/4-in

Lumber

Parallel-to-Grain

Monotonic III 11S

Monotonic III 10S


III 12S

Specimen FabricationThe full test program required four samples of matched specimens. Matched samples were

obtained by cutting four replicates of each component from adjacent locations in a single board ofsouthern pine lumber. This matching technique provides specimens in each sample with as close toidentical physical characteristics as possible. Obvious local variations such as knots or splits wereavoided in choosing the locations of each set of four components. Matched components were thenmarked so that sets of four "identical" specimens produced four samples, each with 15 or 10 matchedspecimens depending on whether the fasteners were nails or bolts, respectively. Results of tests onthree of the four matched samples are presented in this report. The fourth matched sample was testedusing the SPD procedure, and the results are presented in subsequent reports.

Nail ConnectionsNailed connections were fabricated and then placed in an environmental chamber (at 20 C0

(68 F) and 65% relative humidity) for a minimum of 14 days to allow for relaxation of wood fibers0

around the nail and to achieve approximate equilibrium moisture content. This conditioning time


provided a more accurate representation of a nailed connection that has been in service for a periodof time. Nailed connections usually have a higher initial stiffness immediately after assembly becausewood fibers in contact with the nail shank have not relaxed.

Pre-drilled nail holes, meeting the guidelines established in the 1991 NDS, were used to guidethe nails and prevent splitting of the wood members during driving with a hand-held hammer for allexcept one sample. The 1991 NDS allows a pre-drilled hole no more than 75% of nail diameter forwood with a specific gravity less than 0.60. Therefore, connections using 10d common nails werepre-drilled with a 1/16-inch hole, or 42% of nail diameter, and connections using 16d common nailswere pre-drilled with a 3/32-inch hole, or 58% of nail diameter. For 18-gauge steel plate to 2x4connections, a 9/64-inch hole (95% of nail diameter) was pre-drilled in the steel plate. Members usedin the testing had actual average specific gravities ranging from 0.48 to 0.62 depending upon thegrade and size of lumber used. One sample of lumber-to-lumber connections, using 16d commonnails, was fabricated without drilling pilot holes.

Bolted ConnectionsBolted connections were fabricated immediately prior to testing. A bolt hole that was 1/16-

inch larger than the bolt was used for both wood and steel members of all bolted connections. Thiswas in accordance with assembly tolerances given in the 1991 NDS and 1989 Manual of SteelConstruction, Allowable Stress Design published by the American Institute of Steel Construction.All bolt holes were centered between the edges of members and drilled with high speed steel drill bitsto ensure smoothness and uniformity. In all connection configurations, end and edge distancesexceeded minimum requirements given in the 1991 NDS for use of full design values, and standardA307 mild carbon steel bolts or their equivalent were used.

Active members of the connections were held by a gripping fixture attached to the testingmachine. For bolted connections a grade-eight bolt was inserted through the gripping fixture into apre-drilled hole of the same diameter to prevent any slipping between the wood or steel member andthe grip. Stationary members of the connections were blocked to prevent any movement.

Test EquipmentAll tests were conducted in the Wood Engineering Laboratory of the Brooks Forest Products

Research Center at Virginia Polytechnic Institute and State University. Two MTS servohydraulic testmachines were used to conduct displacement-controlled monotonic tests and load-controlled cyclictests. Displacements and loads were measured using two linear variable differential transformers(LVDT) that were attached to the sides of specimens to measure connection slip, and load cellsattached to the MTS actuators. Data was acquired using commercial data acquisition software ona micro computer in the engineering laboratory. Acquired data was analyzed using commercialspreadsheet software.

Test specimens were held in place and guided by a steel fixture to prevent rotation that wouldresult in forces other than pure shear being applied to the specimen. Figure 1 shows a diagram of thetest fixture. One important aspect of the fixture alignment is that the center of the load cell is in theconnection shear plane. This minimizes any moment introduced into the specimen. Rollers areincluded in the fixture to minimize the effects of friction between the fixture and the moving side ofthe specimen.

Loadcell

GripRollers

Rollers

Specimen

LVDT

Pins topreventslippage,if required


Figure 1: Test fixture used for connection lateral load tests.

Monotonic LoadingMonotonic connection tests were conducted using a displacement-controlled rate of

0.1 in./min. A sample of specimens for each connection type was tested to ultimate capacity, or toapproximately one inch displacement if catastrophic failure did not occur prior to reaching a limitingdisplacement. Monotonic test specimens were not subjected to any prior cyclic loading and provideda control group tested with traditional procedures. Key information obtained from these tests wereyield load and displacement, defined by the five-percent of dowel diameter offset method describedin the 1991 NDS. Also, initial stiffness, capacity, displacement at capacity, and ductility weredetermined. (Ductility is defined as the ratio of displacement at capacity to yield displacement.)Monotonic tests were conducted for both parallel-to-grain and perpendicular-to-grain orientations,with data acquired at five points per second.


Cyclic LoadingLoad-controlled cyclic tests were performed at a rate of 1 Hz. Nailed connections were

subjected to fully reversing cyclic loading at two load levels: the 1991 NDS nominal design load for30 cycles, followed by loading at 1.75 times design load for 15 cycles. The 1.75 factor consists ofthe load duration factor, 1.6, multiplied by the diaphragm factor, C = 1.1. One nailed connectiondi

geometry, with 15 replicates, was tested with an additional 8 cycles at 2.0 times the 1991 NDSnominal design load. Bolted connections were cycled at three load levels: the 1991 NDS nominaldesign load for 30 cycles, followed by cycling at 1.6 times nominal design load for 15 cycles, and thenat 2.0 times nominal design load for 8 cycles. Upon completion of the cyclic load regime, allspecimens were tested under monotonic loading, to either catastrophic failure or a displacement of1.0 inches.

Data was acquired at a rate of 100 points per second for all cyclic tests. This high rate ofacquisition ensured an accurate representation of the complete hysteresis for analysis. The time lapsebetween changes in cyclic load levels, and between the final cycling level and the monotonic loadingat the end of cycling, was only long enough to change settings on the MTS and reset the dataacquisition program.

RESULTS AND DISCUSSION

Property DefinitionsSix properties that define monotonic performance of the connections were determined for

each specimen. These properties were 1) initial stiffness, 2) yield load, 3) yield displacement,4) capacity, 5) displacement at capacity, and 6) ductility. Figure 2 illustrates five of the sixproperties. Initial stiffness is the slope of the initial section of the load-displacement curve. Yieldload and displacement are defined by the point where a line drawn parallel to the initial stiffness,but offset along the displacement axis by 5% of fastener diameter, intersects the load-displacementcurve. Yield displacement is the distance between the intersection of the initial stiffness line withthe displacement axis and the displacement corresponding to the yield load.

Capacity of the connection is defined as the ultimate load or the load resisted at a slip of 1.0inches. The load at 1.0 inch slip is used to define capacity for two reasons. First, if a connection ina real structure were to slip as much as 1.0 inch, load would be most likely transferred to otherlocations in the structure due to load sharing. Second, the 1.0 inch displacement is close to themaximum displacement that the fixture could tolerate and continue to maintain the specimen's correctalignment.

Ductility of a connection is a measure of how much displacement the connection can sustainafter yielding and not fail. This property is one indicator of how a structure will perform during anearthquake. Higher ductility of structures provides a means to sustain deflections imposed during aseismic event. Ductility is defined as displacement at capacity (as defined in the previous paragraph)divided by yield displacement, and always has a value greater than 1.0.

> 'D

2BP× 100


(1)

Figure 2. Typical monotonic load-deflection curve for a connection with properties defined.

Three properties were used to define cyclic performance of the connections. These propertieswere 1) hysteretic damping, 2) equivalent viscous damping, and 3) cyclic stiffness. Figure 3shows a typical hysteresis for a nail connection along with information required to calculate the threeproperties. Figure 4 show a typical hysteresis for a bolt connection with similar information requiredfor calculating the properties.

In Figure 3, the area enclosed by the load-deflection curve during one cycle representshysteretic damping. This is a measure of actual energy dissipated by the connection. The valuesfor this property are determined by integrating the area inside the hysteresis loop using a Simpson'srule algorithm.

Connection potential energy is defined as the area enclosed by triangles OMN and OQP andare used to calculate the equivalent viscous damping for the connection with the equation

where:> = the equivalent viscous damping ratio in percentD = the hysteretic damping (dissipated energy during one cycle, in-lb)P = the potential energy for the same cycle (in-lb)

A

BCE

D

HYSTERESIS

POTENTIAL ENERGY

CYCLIC SLOPE

DISPLACEMENT


Figure 3. Typical hysteresis for a nail connection with properties defined.

Figure 4. Typical hysteresis for bolt connection with properties defined.


The equivalent viscous damping is an indicator of how much energy an equivalent singledegree-of-freedom, mass-dashpot system would dissipate, and is a useful property for numericalmodeling structural systems or for making comparisons between connections manufactured ofdifferent materials.

Finally, cyclic stiffness is defined as the slope of the line connecting points Q and M shownin Figure 3. This property indicates how the connection "softens" or degrades during the loading.

The definitions of viscous damping and cyclic stiffness are different for bolt connections dueto "slop" in the connection associated with holes being 1/16-inch larger than the bolts. For boltedconnections, two potential energies were defined. The first includes the effect of oversized holes(areas MNO and OQP shown in Figure 4), and the second excludes the effect of oversized holes(areas LMN and RQP shown in Figure 4). This change results in two calculated values of equivalentviscous damping for bolt connections. Cyclic stiffness was also defined for the two cases, i.e.including the effect of oversized holes (slope of line QM shown in Figure 4) and excluding the effectof oversized holes (the average of the slopes of lines LM and RQ shown in Figure 4). The definitionof hysteretic energy was not changed from that used for the nail connections and is equal to the areaenclosed by the load-deflection curve for one complete cycle.

Changes in the definition for equivalent viscous damping and cyclic stiffness were made toprovide information on the bounds of expected cyclic response of connections used in real structures.The 1991 NDS provides for bolt holes to be a minimum of 1/32-inch and a maximum of 1/16-inchoversize in Section 8.1.2.1. Therefore, the two values calculated for each property provideinformation on the bounds of possible performance of connections manufactured within the allowanceof the 1991 NDS provisions. While total exclusion of the effects of oversized bolt holes may not bea realistic assumption since the minimum size for the holes is 1/32-inch oversize, it is a conservativeassumption for determining bounds of performance. Excluding the effect of oversized holes resultsin overestimated values for cyclic stiffness.

After the cyclic load regime was completed, each specimen was tested monotonically untileither catastrophic failure occurred or a slip of 1.0 inch was reached. This is the same failuredefinition that was used for monotonic only tests of specimens not subjected to cyclic loading. Twoproperties were determined from the post-cyclic monotonic tests; capacity and the correspondingdisplacement. These two properties were then compared to results of the tests where onlymonotonic loading was used, to determine if the prior cyclic load history affected the performanceof the connections.

Nailed Connection ResultsAverage values for properties of interest for the nail connection tests and the corresponding

coefficients of variation (COV) are presented in Table 3. Both parallel- and perpendicular-to-grainproperties are included in the table to allow for comparisons between performance in the two typesof tests. The monotonic results listed in this table are for those specimens tested with and withoutany prior cyclic testing.

Defining capacity with both strength and maximum displacement criteria affected themagnitude of the capacity as well as the displacement at capacity results. If capacity had been definedas only the catastrophic failure load, the average value for the test parameter would have been higher.


The NDS yield loads, shown toward the bottom of Table 3, were determined by multiplyingthe nominal design values by the corresponding diameter coefficient, K , given for Equations 12.3-1D

through 12.3-4 in the 1991 NDS. Average yield loads obtained for parallel-to-grain nailedconnections not subjected to prior cyclic loading ranged from 29 percent lower to 15 percent higherthan the yield loads associated with nominal design values listed in the 1991 NDS. This discrepancyis partially due to the average specific gravities and moisture contents of the tested connectionmembers being slightly higher than the values assumed in the 1991 NDS for southern pine. Frictionin the test fixture and different end fixity conditions from those used in the tests on which the NDSvalues are based could also contribute to the discrepancies. Finally, yield strengths for nails and/orsteel plates may have been different than values assumed in the 1991 NDS. The coefficient ofvariation (COV) in the 5 percent diameter offset bending yield strength of common nails is knownto be as high as 12% COV (Loferski and McLain, 1991).

Table 3: Averages and coefficients of variation (%) for monotonic tests of nailed connectionsfabricated with pilot holes..

2x4/2x4 15/32" Plywood/2x4 18 Gage steel Plate/2x410d Common Nail16d Common Nail 10d Common Nail

Monotonic Parallel- Perpendicular- Parallel- Perpendicular- Parallel- Perpendicular-Parameters to-Grain to-Grain to-Grain to-Grain to-Grain to-GrainYield 241 lbs. 213 lbs. 160 lbs. 161 lbs. 305 lbs. 309 lbs.Load: (16.4) (8.8) (22.4) (11.1) (28.0) (14.6)Yield 0.020 in.0.021 in. 0.019 in. 0.020 in. 0.015 in. 0.014 in.Displacement: (14.1)(33.3) (18.9) (21.6) (12.7) (12.2)Initial 19200 lbs./in.21800 lbs./in. 15700 lbs./in. 14400 lbs./in. 44000 lbs./in. 46300 lbs./in.Stiffness: (24.4)(42.9) (39.7) (33.2) (36.8) (36.0)Capacity: 410 lbs. (7) 455 lbs. (0) 369 lbs. (6) 391 lbs. (0) 527 lbs. (0) 614 lbs. (0)

(14.6) (9.7) (12.2) (11.7) (11.5) (12.9)Displacement at 0.617 in. 0.415 in. 0.698 in. 0.428 in. 0.206 in. 0.231 in.Capacity: (60.5) (23.9) (42.6) (29.4) (30.8) (19.6)Ductility: 30.1 21.4 38.2 22.1 14.3 16.4

(66.8) (25.0) (45.5) (27.3) (30.8) (30.6)

Yield Mode: IV III IIIs s

1991 NDS 154 lbs. 101 lbs. 121 lbs.Nominal Value:1991 NDS 339 lbs. 222 lbs. 266 lbs.Yield Load:

Note: Numbers in parenthesis to the right of the capacities are the number of specimens in which capacity wascontrolled by the limiting displacement.

Table 4 shows the monotonic test results for 2x4-to-2x4 connections fabricated with andwithout pilot holes. As shown, the yield load for driven nail connections is lower and the associateddisplacement is higher than those connections fabricated with pilot holes. The initial stiffness ofdriven nail connections is also lower. These three parameters indicate that the pilot holes improvethe initial performance of the connections by reducing some of the localized spreading of the woodfibers surrounding the nail, and therefore provide stiffer resistance to lateral deformation. However,the ultimate capacity and ductility of connections with driven nails are higher than for connectionswith pilot holes. This indicates that the friction provided by the spread wood fibers surrounding the


nail is higher when the connection is loaded to its ultimate capacity and pilot holes are not used.

Table 4: Averages and coefficients of variation (%) for monotonic tests of 16d common nailedconnections fabricated with and without pilot holes..

2x4/2x4 2x4/2x416d Common Nail 16d Common Nail

Monotonic Parallel-to-Grain Parallel-to GrainParameters With Pilot Holes Without Pilot Holes (Driven)Yield 241 lbs. 178 lbs.Load: (16.4) (39.0)Yield 0.021 in. 0.026 in.Displacement: (33.3) (44.8)Initial 21800 lbs./in. 12174 lbs./in.Stiffness: (42.9) (48.0)Capacity: 410 lbs. (7) 427 lbs. (0)

(14.6) (13.0)Displacement at 0.617 in. 0.420 in.Capacity: (60.5) (45.1)Ductility: 30.1 43.6

(66.8) (41.7)

Yield Mode: IV

1991 NDS 154 lbs.Nominal Value:1991 NDS 339 lbs.Yield Load:


Table 5 shows the capacity and associated displacement for the monotonic tests on specimenswith and without prior cyclic loading. Only specimens with the load applied parallel-to-grain wereused to investigate the effects of cyclic loading on connection performance. Capacity for allconnections was higher for the connections that were loaded cyclicly prior to being testedmonotonically to failure. This may have been due to cold working of the nails during the cyclicloading, since there was no difference in average moisture content for the two samples and averagespecific gravity for the cyclic samples was either equal to or lower than the monotonic sample.

Table 5: Capacity, associated displacement, and their associated COV (%) of nail connections withand without prior cyclic loading.

2x4/2x4 15/32" Plywood/2x4 18 Gage Steel Plate/2x416d Common Nail 10d Common Nail 10d Common Nail

Parameter Not Cycled Cycled Not Cycled Cycled Not Cycled CycledCapacity: 410 lbs. (7) 439 lbs. (5) 369 lbs. (6) 374 lbs. (6) 527 lbs. (0) 532 lbs. (0)

(14.6) (10.9) (12.2) (11.2) (11.5) (9.5)Displacement 0.617 in. 0.506 in. 0.698 in. 0.732 in. 0.206 in. 0.259 in.at Capacity: (60.5) (70.5) (42.6) (35.8) (30.8) (23.6)



Table 6 lists averages and coefficients of variation for specific gravity and moisture contentof the nailed connections. Average specific gravities of the members used in 2x4-to-2x4 connectionsand plywood-to-2x4 connections were slightly higher than the 0.55 given in the 1991 NDS, and theaverage specific gravity of wood used for steel plate-to-2x4 connections was significantly higher.Dimension lumber used in these tests was primarily graded No.1 Dense or Dense Select Structural,which will have a higher than average specific gravity. Moisture content and specific gravity sampleswere taken from the immediate vicinity of the nail hole for approximately half of the tested specimens,and were determined using ASTM D-2016 and D-2395 standard procedures.

Table 6: Averages and coefficients of variation (%) for percent moisture content and specific gravityin nailed connections.

2x4/2x4 Parallel-to-grain Perpendicular-to-grain

16d nail Monotonic Cyclic Monotonic

Stationary Moving Stationary Moving Stationary Moving

Member Member Combined Member Member Combined Member Member Combined

MC 14.5 15.5 15.0 14.0 15.5 14.8 12.8 13.8 13.3

(w / Pilots) (9.1) (3.8) (7.4) (9.7) (7.5) (9.8) (7.0) (6.8) (7.6)

SG 0.55 0.60 0.58 0.55 0.58 0.56 0.57 0.55 0.56

(w / Pilots) (9.8) (10.6) (10.9) (9.2) (10.3) (10.7) (13.6) (10.2) (11.8)

MC 14.0 14.0 14.0

(w/0 Pilots) (7.0) (6.0) (7.0)

SG 0.56 0.59 0.58

(w/o Pilots) (9.0) (8.0) (9.0)

15/32" Parallel-to-grain Perpendicular-to-grain




MC 13.1 13.4 14.0

(5.1) (1.3) (8.1)

SG 0.57 0.53 0.54

(10.4) (14.2) (12.4)

18 ga. steel Parallel-to-grain Perpendicular-to-grain




MC 11.3 12.1 12.3

(5.9) (5.0) (3.1)

SG 0.62 0.61 0.63

(5.0) (3.9) (8.8)


Parallel-to-Grain Orientation - Nails Tested MonotonicallyAverage yield displacements for the three types of nailed connections indicate a joint slip at

yield ranging from 0.015 inches to 0.021 inches in the parallel-to-grain orientation. The reason forlower yield displacement in the steel plate-to-2x4 connection can be seen graphically in Figure 2. Asthe slope of the initial linear region of the load-displacement curve becomes steeper, indicating higherstiffness, the corresponding yield displacement must become smaller. Yield displacements,determined by the 5 percent of diameter offset method, were higher for wood-to-wood connections.

Connection capacities for the parallel-to-grain specimens without and with prior cyclic loadingwere higher than 1991 NDS nominal design loads. Corresponding apparent factors-of-safety weredetermined by dividing the experimental capacities by the 1991 NDS nominal design loads. Resultingapparent factors-of-safety are shown in Table 7, and range from 2.7 to 5.1. Table 7 also shows theapparent factors-of-safety for seismic and wind design. To obtain seismic design apparent factors-of-safety, seismic design values for the connection were determined by multiplying the nominal designvalues by the 1991 NDS load duration and diaphragm adjustment factors (C =1.6 and C =1.1).D di

Connection capacities were then divided by the seismic design value. As shown in Table 7, apparentfactors-of-safety for the proposed seismic design range from 1.5 - 2.9 for specimens loadedmonotonically, and from 1.6 - 2.5 for cyclicly loaded specimens. These results indicate that factors-of-safety for nailed connections were not affected by the cyclic loading experienced prior to themonotonic loading to failure. Due to the high ductility and energy dissipation caracteristics of nailedconnections, a factor-of-safety of 1.5 for nails used to attach sheathing in diaphragms should besufficient.

Average capacities for the 2x4-to-2x4 and plywood-to-2x4 connections would have beenhigher had the limiting displacement not been reached before catastrophic failure occurred. Capacitywas determined by the limiting displacement criteria for more than one-third of the individual wood-to-wood connections tested parallel-to-grain. Capacity was determined by catastrophic failure forall of the steel plate-to-2x4 connections; in this case, capacity is a good indicator of ultimate loadcapacity.

Higher levels of variation in displacement at capacity occurred in 2x4-to-2x4 and plywood-to-2x4 connections because many specimens continued to increase in load until the limitingdisplacement was reached and the test was stopped, rather than a catastrophic failure occurring.Capacity for all steel plate-to-2x4 connections and for the perpendicular-to-grain orientation of wood-to-wood connections was determined by ultimate load.

The limiting displacement criteria also had an effect on variation in ductility. Connections thatwere affected by the limiting displacement would have had higher ductilities if the monotonic testshad been load controlled rather than displacement controled. Average ductility of 2x4-to-2x4 andplywood-to-2x4 nailed connections was 29.2 and 27.5, respectively, while steel-to-2x4 connectionshad a ductility of only 13.7. The difference in ductility is directly associated with the lowdisplacement at capacity for the 18-gauge steel plate-to-2x4 connection. This low displacement atcapacity is related to the mode of failure observed. The steel plate showed localized buckling aroundthe nail head at low displacements. This buckling caused the capacity to be reached at lowerdisplacement levels than in the tests of connections with wood or plywood side members. In contrast,connections with wood or plywood side members showed localized crushing of wood material aroundthe fastener which resulted in a gradual failure and larger displacements at capacity being observed.


While these two modes of failure are different, calculated ductility would translate into similarresponse of full structures and therefore the values should directly compared if connection influenceon structural performance is of interest.

Table 7: Apparent factors-of-safety for nail connections.

2x4/2x4 15/32" Plywood/2x4 18 Gage Steel/2x4

16d Common Nail 10d Common Nail 10d Common Nail

Parallel-to-grain

Average Capacity (w / Pilots) 410 lbs. 369 lbs. 527 lbs.

Average Capacity (w/oPilots)

427 lbs.

1991 NDS Design Value 154 lbs. 101 lbs. 121 lbs.

Resulting Factor of Safety 2.7 3.7 4.4

Wind/Seismic Design Value 246 lbs. 162 lbs. 194 lbs.

Resulting Factor of Safety (w / Pilot Holes)

1.7 2.3 2.7

Resulting Factor of Safety (w / o Pilot Holes)

1.7

Perpendicular-to-grain

Average Capacity 455 lbs. 391 lbs. 614 lbs.





Post-Cyclic






For nailed connections under monotonic loading, both initial stiffness and capacity increasedas the strength and local stiffness of the side and/or active member increase. As shown in Table 3,


the plywood -to-2x4 connection has a lower initial stiffness and capacity than did the 18-gauge steelplate-to-2x4 connection. Increased stiffness of the steel plate and increased penetration of the nailin the main member are why this connection was stiffer and stronger; this behavior adds credibilityto the yield model assumed for connection design in the 1991 NDS.

Perpendicular-to-Grain Orientation - Nails Tested MonotonicallyA second set of matched specimens for each nailed connection type was tested in a

perpendicular-to-grain orientation. These results are presented in the second column for eachconnection type in Table 3. Statistical t-tests ("=0.025, two-tailed test) were used to test ahypothesis that average values for each parameter for parallel- and perpendicular-to-grain orientationswere equal. The t-tests indicated no significant differences between parallel- and perpendicular-to-grain orientations for yield load, yield displacement, and initial stiffness for the nailed connectionstested. One exception was the difference in average yield load in 2x4-to-2x4 connections for theparallel- versus perpendicular-to-grain orientation. The 2x4-to-2x4 connections had a 12 percentlower average yield load in the perpendicular-to-grain orientation, while yield displacement and initialstiffness were not significantly different. This is due to the degree of curvature in the load-displacement curve after the initial linear region. The perpendicular-to-grain orientation for thisconnection exhibited a greater curvature in the non-linear range than did the parallel-to-grainorientation, resulting in a lower yield load while having similar initial stiffness.

T-tests on average capacities indicated no significant difference in mean capacity betweenparallel-to-grain and perpendicular-to-grain orientations for plywood-to-2x4 connections. There wassufficient evidence to reject the hypothesis of equivalency for the 2x4-to-2x4 and steel plate-to-2x4connections. However, all connections loaded perpendicular-to-grain reached a capacity caused bycatastrophic failure, whereas some wood-to-wood parallel-to-grain connections were governed bythe limiting displacement criteria. Thus, catastrophic capacities of these specimens loaded parallel-to-grain would be higher. The displacement criteria imposed on this test must be considered whenevaluating the t-test on the capacity parameter for the two orientations in wood-to-wood connections.Both parallel-to-grain and perpendicular-to-grain orientations of steel plate-to-2x4 connectionsreached a catastrophic failure-controlled capacity before the limiting displacement was reached,therefore, the t-test for this connection can be considered on its face value and indicates that thisconnection may be stronger in the perpendicular-to-grain orientation.

Since more individual perpendicular-to-grain wood-to-wood specimens reached catastrophicfailure-controlled displacement at capacity than did the parallel-to-grain specimens, there was acorresponding decrease in average displacement at capacity for wood-to-wood connections orientedperpendicular-to-grain. However, steel plate-to-2x4 connections had an increase in displacementat capacity for the perpendicular-to-grain orientation.

The higher average displacement at capacity for the perpendicular-to-grain orientation of steelplate-to-2x4 nailed connections was due to the way wood crushed around the nail in the main memberfor the two orientations. In the parallel-to-grain orientation, the nail caused crushing parallel-to-grain. This resulted in wood crushing in early wood for a greater distance in the main member. Inthe perpendicular-to-grain orientation, there was less yielding of wood, due to high density latewoodbands, and more nail bending as it was forced to withdraw (or caused the nail head to inbed in theside member). Therefore, it is reasonable to conclude that the perpendicular-to-grain orientation has


a higher displacement at capacity due to higher capacity and withdrawal resistance associated withreduced of wood damage along the grain.

Post-Cyclic Monotonic Tests of Nailed ConnectionsMonotonic tests were conducted on previously cycled specimens, following the end of the last

series of cycles. Results of these post-cyclic tests are presented in Table 5. Displacement at capacitywas determined by first adjusting the post-cyclic monotonic load-displacement curves. Load-displacement curves for the post-cyclic, monotonic tests were shifted so that the displacement at themaximum load, experienced during the last cycle of a cyclic test, equaled the displacement at the sameload for the post-cyclic monotonic load-displacement curves. This was necessary because theLVDT's, used to measure connection slip, had to be repositioned after cyclic testing to allow the fullrange of motion of the instrument to be used for the monotonic tests. Also, as the cyclic tests wereload-controlled, the MTS machine stopped a 0 load at the end of the cycling. Due to the effect ofresidual load, the displacement at which 0 load is reached at the end of the last cycle was a negativedisplacement in relation to the displacement at the beginning of the test.

The three types of nailed connections seemed to exhibit a slight increase in average capacityafter cycling. One contributing factor was the number of specimens in each orientation that reacheda limiting displacement controlled capacity. Statistical t-tests were used to test the hypothesis ofequivalence between average monotonic capacities of specimens with and without prior cyclicloading. Results of t-tests indicated that there was no significant difference in capacities of any nailedconnection type tested. In other words, the prior cyclic loading did not affect the connectioncapacity.

Statistical t-tests also indicated that there was not sufficient evidence to reject the hypothesisof equivalency for 2x4-to-2x4 and plywood-to-2x4 connections, but there was sufficient evidence toreject the hypothesis of equivalency for the average displacements at capacity for steel plate-to-2x4connections. This would indicate that prior cyclic loading increased the displacement at whichcatastrophic failure occurred for the steel-to-wood connection.

Cyclic Properties of Nailed ConnectionsThe initial hysteresis for all cyclic tests was defined as the second cycle beginning as the

hysteretic loop crosses the load axis on the tension side of the cycle and ending as the hysteresisreturns to the same position. The second cycle was used instead of the first because it provides thefirst complete hysteretic loop for analysis rather than including part of the virgin loading curve. Thefinal cycle was defined as the last cycle of a set of cycles at a given load level, beginning as thedisplacement axis is crossed at a negative displacement on the tension side of the cycle. The finalhysteresis loop ends at the same negative displacement on the displacement axis as it began. Sinceall cyclic tests were performed in load control condition, load returned to zero at the end of the testrather than zero displacement. In order to allow a complete hysteresis loop to be analyzed, the finalcycle must begin at zero load and a negative displacement and end at the same point.

Table 8 presents the results of cyclic tests performed on nailed connections. As shown in thetable, the cyclic properties for all three connection types followed similar trends. Increases ordecreases in values for the cyclic properties investigated were observed between the initial and finalcycles at a given load level. Hysteretic energy dissipation increased between the initial and final


cycles at at a given load level for all connection types. The cyclic stiffness decreased for allconnection types with increased cycling. Most of this decrease in stiffness ocurred during the firstthree to four cycles at each load level. Equivalent viscous damping remained fairly constant for allload levels, and ranged from 21.5 - 31.3 percent, with an average of 26.6 percent.

Table 8: Average values and coefficients of variation (%) of cyclic properties for nailed connections.2x4/2x4 15/32" Plywood/2x4 18 Gage Steel Plate/2x4

16d Common Nail 10d Common Nail 10d Common Nail

Cyclic 1.0 NDS 1.75 NDS 1.0 NDS 1.75 NDS 1.0 NDS 1.75 NDS 2.0 NDSParameters 30 Cycles 15 Cycles 30 Cycles 15 Cycles 30 Cycles 15 Cycles 8 CyclesHysteretic Initial: 1.39 in.-lbs. 8.60 in.-lbs. 1.40 in.-lbs. 6.19 in.-lbs. 0.31 in.-lbs. 1.77 in.-lbs. 2.74 in.-lbs.Energy (36.5) (30.9) (30.3) (25.8) (112.3) (59.6) (49.0)

Final: 1.61 in.-lbs. 11.22 in.-lbs. 1.48 in.-lbs. 7.58 in.-lbs. 0.32 in.-lbs. 1.96 in.-lbs. 3.00 in.-lbs.(34.1) (36.7) (29.3) (28.5) (118.4) (55.1) (46.7)

Stiffness Initial: 37600 lbs./in. 15600 lbs./in. 13400 lbs./in. 7900 lbs./in. 117000 lbs./in. 59900 lbs./in. 45700 lbs./in.(66.9) (51.4) (40.7) (35.5) (37.8) (37.5) (39.2)

Final: 32100 lbs./in. 11800 lbs./in. 12000 lbs./in. 6100 lbs./in. 110000 lbs./in. 52000 lbs./in. 42800 lbs./in.(64.1) (56.2) (41.0) (36.7) (38.3) (40.3) (41.8)

Damping Initial: 28.4 % 25.2 % 25.6 % 23.3 % 27.6 % 31.3 % 28.8 %Ratio (23.8) (17.3) (15.1) (11.5) (27.1) (8.5) (12.5)

Final: 28.2 % 23.4 % 23.8 % 21.5 % 26.3 % 29.8 % 29.5 %(19.8) (14.1) (12.2) (10.5) (33.8) (10.1) (11.8)

These trends are not suprising since some damage does occur around the nail during therepeated cycling. Hysteretic damping increased within a given load level from the initial cycle to thefinal cycle as a result of incremental increases in joint slip. Figure 5 shows a typical load-displacementcurve for a nail connection test, and illustrates the increase in joint slip with cycling for the nailedconnections. Increases in hysteretic energy dissipation ranged from 3 to 16 percent at 1.0 timesdesign load, and from 11 to 30 percent at 1.75 times design load. The connections tested at 2.0 timesdesign load had a 9 percent increase in hysteretic energy dissipation. At lower load levels,incremental increases in slip occurred for only the first few cycles. As shown in Figure 5, slipincreases at a decreasing rate with continued cycling at a given load level, with the greatest increasesin slip occurring within the first three cycles. The decreasing rate of slip increase is important as itindicates that the system stabilizes with repeated cycling.

Cyclic stiffness decreased from the initial cycle to the final cycle within a given load level fornailed connections due to increases in joint slip with cycling. Decreases in stiffness occurred at adecreasing rate as the number of cycles increased because incremental increases in displacement weresmaller with successive cycling. Decreases in cyclic stiffness from the initial cycle to the final cycleranged from 6 to 15 percent at the 1.0 times 1991 NDS design load level, and from 13 to 24 percentat the 1.75 times design load level. Connections tested at 2.0 times the NDS nominal design load hada 6 percent reduction in cyclic stiffness from the initial to final cycle.

The effect of cycling on equivalent viscous damping ratio was small and inconsistent, withsome individual specimens having an increase while others decreased. A decline in equivalent viscousdamping is due to the hysteretic damping increasing, as would be expected, due to an increaseddisplacement associated with the higher load. However, potential energy also increased due to higherjoint slip. A decrease in damping ratio indicates a decrease in the numerator of Equation 1, thehysteretic damping, relative to the denominator (2 B times the available potential energy) of a


connection. However, this does not mean that an increase in potential energy of the connection wasmore than the associated increase in hysteretic damping. In fact, the actual hysteretic dampingconsistently increased more than potential energy at the higher load levels.

Figure 5. Typical load-displacement time history for a segment of a load-controlled cyclic test of anail connection.

Bolted Connection ResultsAverage values and COV for the properties of interest obtained from monotonic tests of

bolted connections with no prior cyclic loading are presented in Table 9. Yield loads obtained forthese sets of specimens were from 2 percent lower to 54 percent higher than yield loadscorresponding to 1991 NDS nominal design loads. NDS nominal design loads were converted totheir corresponding yield loads by multiplying the nominal values by the constant in the denominatorof Equations 8.2-1 through 8.2-4 of the 1991 NDS.

Table 10 presents averages and coefficients of variation for moisture content and specificgravity of the bolted connections tested. Moisture content and specific gravity samples were takenfrom every specimen in the immediate vicinity of the bolt hole. Lower yield loads determined for4x4-to-4x4 connection can be partially attributed to the specimens having lower specific gravities thanthe 0.55 assumed for the 1991 NDS. The higher yield loads observed for 2-inch-to-2-inch nominallumber, and steel plate-to-4-inch nominal lumber bolted connections could be due to the bolts havinga higher bending yield strength than assumed for the 1991 NDS. Another factor that may have ledto the higher yield value in the tested connections is the yield strength of the steel plate material mayhave had a higher yield strength than the values assumed by the 1991 NDS. Determination of theyield strength of bolts and steel plates was beyond the scope of this study.


Table 9: Average values and coefficients of variation (%) for monotonic properties of boltedconnections without prior cyclic load history.

2x4/2x4 (2x8) 1/4" Steel/4x4 (4x6) 4x4/4x4 (4x8)3/4" bolt 1/2" bolt 3/4" bolt

Monotonic Parallel- Perpendicular- Parallel- Perpendicular- Parallel- Perpendicular-Parameters to-Grain to-Grain to-Grain to-Grain to-Grain to-GrainYield 2810 lbs. 2550 lbs. 2930 lbs. 2400 lbs. 3470 lbs. 2510 lbs.Load: (19.6) (11.5) (14.4) (15.2) (15.1) (14.1)Yield 0.112 in. 0.168 in. 0.102 in. 0.146 in. 0.144 in. 0.172 in.Displacement: (12.2) (13.0) (21.6) (18.1) (16.8) (22.4)Initial 37600 lbs./in. 19800 lbs./in. 43400 lbs./in. 20500 lbs./in. 32900 lbs./in. 19700 lbs./in.Stiffness: (18.6) (14.1) (30.1) (14.4) (19.0) (26.9)Capacity: 5220 lbs. (3) 5140 lbs. (9) 5360 lbs. (4) 6510 lbs. (10) 6280 lbs. (10) 5000 lbs. (10)

(18.4) (7.6) (16.6) (5.0) (9.3) (11.9)Displacement at 0.735 in. 0.910 in. 0.726 in. 0.921 in. 0.893 in. 0.885 in.Capacity: (20.9) (3.5) (29.2) (3.7) (4.3) (5.5)Ductility: 6.5 5.5 7.5 6.5 6.3 5.4

(17.5) (13.4) (36.8) (21.0) (17.3) (19.6)

1991 NDSNominal Design 800 lbs. 460 lbs. 780 lbs. 500 lbs. 1690 lbs. 960 lbs.Value:

1991 NDS YieldLoad:

2880 lbs 1656 lbs. 2496 lbs 1600 lbs. 5408 lbs. 3072 lbs.

Yield Mode: II II IV III IV IIIM S


Parallel-to-Grain - Bolts Tested MonotonicallyAverage yield displacements for bolted connections ranged from 0.102 inches to 0.144 inches

for the parallel-to-grain orientation. Yield displacement is inversely related to the initial stiffness. Asinitial stiffness of a given connection decreased, the corresponding yield displacement increased. Thesteel plate used as the active member in one of the connection geometries contributed to thatconnection type having the highest average initial stiffness due to the higher bearing strength andstiffness of steel plate. The lowest average initial stiffness occurred in the 4x4 to 4x4 connection,with a contributing factor being the lower average specific gravity for those specimens.

Apparent factors-of-safety for bolted connections are shown in Table 11. As shown inTable 11, apparent factors-of-safety for nominal design loads in the parallel-to-grain orientation were6.5 for 2x4-to-2x4 connections, 6.9 for steel plate-to-4x4 connections, and 3.7 for 4x4-to-4x4connections. When the 1991 NDS design values are multiplied by the load duration factor (C = 1.6)D

for wind and seismic loading, the associated apparent factors-of-safety for the tested connectionswere 4.1, 4.3, and 2.3 for the 2x4-to-2x4, steel plate-to-4x4, and 4x4-to-4x4 connections,respectively.

Table 12 shows the apparent factors-of-safety for bolted connections loaded in theperpendicular-to-grain direction. As expected, the perpendicular-to-grain orientation specimens hadapparent factors-of-safety that were significantly higher than those calculated for the parallel-to-grainorientation.


Table 10: Averages and coefficients of variation (%) for percent moisture content and specificgravity for bolted connections.

2x4/2x x8) Parallel-to-grain Perpendicular-to-grain

¾” Bolt Monotonic Cyclic Monotonic



MC 12.6 12.3 12.5 13.0 12.5 12.8 10.6 13.3 12.0

(9.8) (9.8) (9.8) (8.1) (10.5) (9.2) (6.9) (5.9) (13.1)

SG 0.54 0.59 0.57 0.56 0.61 0.59 0.50 0.58 0.54

(12.5) (10.0) (11.6) (13.4) (10.1) (12.2) (5.0) (14.0) (13.3)

¼@ Steel/4x Parallel-to-grain Perpendicular-to-grain

½@ Bolt Monotonic Cyclic Monotonic



MC 10.6 11.0 13.5

(6.2) (3.2) (4.8)

SG 0.54 0.54 0.51

(15.9) (16.5) (2.9)

4x4/4x Parallel-to-grain Perpendicular-to-grain

¾@ Bolt Monotonic Cyclic Monotonic



MC 19.6 15.8 17.7 19.4 15.7 17.5 16.2 20.0 18.1

(16.2) (4.4) (16.8) (12.1) (4.6) (14.2) (1.8) (17.5) (17.1)

SG 0.48 0.52 0.50 0.49 0.52 0.50 0.48 0.50 0.49

(8.8) (11.5) (10.7) (10.0) (14.0) (12.1) (9.5) (5.9) (8.1)


Table 11: Apparent factors-of-safety for bolt connections loaded monotonically in the parallel-to-grain direction.

2x4/2x4 (2x8) 1/4" Steel/4x4 (4x6) 4x4/4x4 (4x8)

3/4" Bolt 1/2" Bolt 3/4" Bolt

Parallel-to-grain






Post-Cyclic






Table 12: Apparent factors-of-safety for bolted connections loaded monotonically in theperpendicular-to-grain direction.

2x4/2x4 (2x8) 1/4" Steel/4x4 (4x6) 4x4/4x4 (4x8)

3/4" Bolt 1/2" Bolt 3/4" Bolt

Perpendicular-to-grain







The limiting displacement criteria, used as part of the definition of failure, affected values forcapacity, displacement at capacity, and ductility of bolted connections tested. About one-third of the2x4-to-2x4 and steel plate-to-2x4 connections tested parallel-to-grain with no prior cyclic loadingwere considered as failed when the limiting displacement was reached. All of the 4x4-to-4x4connections were considered to have failed when the limiting displacement was reached. Evidenceof the effect of the displacement criteria is shown in Table 9 by the lower variation in capacity for thisconnection. The limiting displacement criteria had the greatest effect on capacity for the 4x4-to-4x4connections, and higher capacities would have been seen if this criteria had not been used.

Average displacements at capacity were relatively high. The lowest variation in averagedisplacement at capacity was observed in 4x4-to-4x4 connections because all of these specimens weregoverned by the limiting displacement. Actual displacements at capacity for bolted connections thatwere governed by the limiting displacement were less than 1.0 inch due to the bolt hole oversize beingsubtracted. The total stroke of the test machine crosshead was 1.0 inch or greater. High averagedisplacements at capacity for the other two bolted connection types reflect the observation thatcatastrophic failure occurred in the form of splitting, at relatively high displacements.

Bolted connection end distances were between 1/2" and 3/4" greater than the minimum enddistances required for use of the full NDS design value. Even with this requirement being adheredto, catastrophic failure occurred in the form of splitting of the wood members in the 2x4-to-2x4 andsteel plate-to-2x4 connections. Greater end distances in the tested connections would have reducedthe occurrence of splitting of the member, and thereby resulted in even higher capacities andassociated displacements.

Ductility, defined as the ratio of displacement at capacity to displacement at yield, was lowerfor bolted connections than nailed connections due to the higher average yield displacements forbolted connections. This property was also affected by the limiting displacement criteria and thepresence of the oversize bolt holes.

Perpendicular-to-Grain - Bolts Tested MonotonicallyA sample for each bolted connection type was tested with the stationary member oriented so

that the load acted perpendicular-to-grain. Results of these tests are presented in Table 9. Loweryield loads for the perpendicular-to-grain orientations are due to the effect of grain orientation onlarger diameter dowel connections, such as bolts. Connections tested perpendicular-to-grain hadaverage yield loads between 18 percent lower and 54 percent higher than the corresponding 1991NDS yield loads. As in the parallel-to-grain orientation, yield loads observed in these tests were notidentical to the values used in the 1991 NDS due to possible differences in bolt bending yieldstrengths and differences in specific gravity. Higher bolt bending yield strengths may explain thehigher observed yield loads even with lower average specific gravities for the tested connections.Steel plate-to-4x6 connections had an average main member specific gravity of 0.51 (the 1/4" steelplate was the side member), yet the tested average yield load was 50 percent higher than thecorresponding NDS value. The 2x4-to-2x8 connections were yield mode II connections andtherefore bolt bending yield strength would not affect the results if they were higher than the assumedvalue. Higher values determined from these tests may also be due to the somewhat subjectiveprocedure used for determining the initial stiffness line on load-displacement curves. Determinationof the initial stiffness line directly affects yield load and displacement.


Average yield displacements for perpendicular-to-grain bolted connections were higher thanfor parallel-to-grain orientations due to lower initial stiffness seen in the perpendicular-to-grainorientation. Lower initial stiffness was due to the effect of grain direction on the initial response oflarger diameter dowels such as bolts. In the perpendicular-to-grain orientation, the bolt is primarilycompressing wood fibers in their weakest direction. Compression parallel-to-grain is a stronger woodmechanical property than compression perpendicular-to-grain, therefore dowel bearing strength ofwood for bolts is higher in the parallel-to-grain orientation.

As shown in Table 11, average capacities of bolted connections loaded perpendicular-to-grainresulted in apparent factors-of-safety of 11.2, 13.0, and 5.2 for the 2x4-to-2x8, steel plate-to-4x6,and 4x4-to-4x8 connections, respectively. If NDS nominal design loads are multiplied by the windand seismic load duration factor, C = 1.6, the apparent factors-of-safety were 7.0 for 2x4-to-2x8D

connections, 8.1 for 1/4" steel plate-to-4x6 connections, and 3.3 for 4x4-to-4x8 connections. Capacities of specimens loaded perpendicular-to-grain were governed by the limiting

displacement criteria for all specimens in each of the three connection geometries. This is reflectedby the low variation for this parameter seen in Table 9. Statistical t-tests indicated a significantlyhigher average capacity for steel plate-to-4x6 connections (perpendicular-to-grain) versus steel plate-to-4x4 connections (parallel-to-grain). The 4x4-to-4x8 connection had an average capacity that wassignificantly lower in the perpendicular-to-grain orientation than parallel-to-grain. A factor that mayhave affected this was low specific gravity of 4x8 stationary members. Statistical hypothesis testingindicated no significant difference in average capacity for 2x4-to-2x8 connections loadedperpendicular-to-grain versus their parallel-to-grain counterparts.

Average displacement at capacity for perpendicular-to-grain orientation was higher thanaverage displacement at capacity for parallel-to-grain orientations for 2x4-to-2x8 and steel plate-to-4x6 connections due to the fact that all of perpendicular-to-grain specimens had capacity determinedby the limiting displacement, while only about one-third of parallel-to-grain specimens did.Coefficients of variation for the displacements at capacity were also significantly lower than the valuesfor parallel-to-grain orientations for all but 4-by-to-4-by connections. Both orientations of 4-by-to-4-by connections experienced a capacity determined by the limiting displacement, as shown by thesimilarity of the values shown in Table 9.

Ductility values were lower for the perpendicular-to-grain orientations than for the parallel-to-grain orientations since they were more affected by the increase in yield displacement than by theincrease in displacement at capacity. Yield displacement properties are governed by the initialstiffness, and since bolts connections have lower stiffness in the perpendicular-to-grain direction, yielddisplacement is significantly higher in this orientation than when the load is parallel-to-grain.

Post Cyclic - Bolts Tested MonotonicallyTables 11 and 13 show results from the post-cyclic monotonic test conducted on bolt

connections. Table 11 shows the apparent factors-of-safety for bolted connections loadedmonotonically after being loaded cyclicly to three magnitudes of load, 1.0, 1.6, and 2.0 times the 1991NDS nominal design value. Apparent factors-of-safety associated with the post-cyclic specimenswere equal to or higher than those calculated for parallel-to-grain specimens with no prior loading,indicating that prior cyclic load history had no effects on capacity of the connections.


Table 13: Average capacity, associated displacement, and COV (%) for bolted connections loadedmonotonically in the parallel-to-grain direction, with and without prior cyclic loading.

2x4/2x4 1/4" Steel/4x4 4x4/4x43/4" bolt 1/2" bolt 3/4" bolt

Parameter Not Cycled Cycled Not Cycled Cycled Not Cycled CycledCapacity: 5220 lbs. (3) 5938 lbs. (1) 5360 lbs. (4) 5626 lbs. (6) 6280 lbs. (10) 6244 lbs. (10)

(18.4) (8.6) (16.6) (14.0) (9.3) (7.9)Displacement 0.735 in. 0.828 in. 0.726 in. 0.826 in. 0.893 in. 0.936 in.at Capacity: (20.9) (12.1) (29.2) (19.7) (4.3) (3.2)

Note: Numbers in parenthesis to the right of the capacites are the number of specimens in which capacity wascontrolled by the limiting displacement.

Table 13 Shows the capacity and associated displacement for monotonic tests on specimenswith and without prior cyclic loading. Post-cyclic test specimens had been subjected to 30 cycles at1.0 times the 1991 NDS nominal design load, 15 cycles at 1.6 times the nominal design load, and 8cycles at 2.0 times the nominal design load. T-tests conducted on average capacities of post-cyclicspecimens indicated no significant difference between average capacities of those specimens that hador had not been subjected to prior loading.

The number of specimens that reached a limiting displacement versus a catastrophic failurealso affected average capacities and corresponding displacements. Limiting displacements for boltedconnections were less than 1.0 inch because slip due to bolt hole oversize was subtracted from theoverall displacement, which was greater than 1.0 inch. Fewer 2x4-to-2x4 connection specimensreached the limiting displacement during monotonic testing after cycling. However, more of steelplate-to-4x4 connections loaded cyclicly reached the limiting displacement than specimens not loadedprior to monotonic testing. The 4x4-to-4x4 bolted connection capacities for all specimens weredetermined by the limiting displacement criteria.

Displacements at capacity for the post-cyclic tests were determined by first adjusting thedisplacements of post-cyclic monotonic load-displacement curves. The curves were shifted along thedisplacement axis so that the point of maximum load obtained during the last cycle of the cyclic testscoinsided with the monotonic curve. This allowed the virgin loading curve to be accuratelydetermined in the post cyclic tests. An initial stiffness line was fit tangent to the initial cycle at the1.0 times the nominal design load level. Where the initial stiffness line intersected the displacementaxis was the reference point, or zero displacement location, for determining the displacement atcapacity values. T-tests on displacement at capacity for 2x4-to-2x4 and steel-to-2x4 connection typesindicated no significant difference between specimens with and without prior cyclic loading. The 4x4-to-4x4 connection type did indicate a statistical difference in the displacement property. However,this property was affected by themaximum displacement criteria as none of the 4x4-to-4x4connections experienced a catastrophic failure, and the difference in the average values is small andhas no practical significance.

Cyclic Properties of Bolted ConnectionsAverage values and the coefficients of variation for cyclic properties of bolted connections

are shown in Table 14. As defined in the Property Definitions section, cyclic stiffness and equivalentviscous damping were calculated for two conditions, including and excluding the effects of theoversized bolt hole. These two values can be considered as bounds on the expected performance of

Table 14: Averages and coefficients of variation (%) for bolted connections subjected to load-controlled cyclic loading.2x4/2x4 1/4" Steel/4x4 4x4/4x43/4" bolt 1/2" bolt 3/4" bolt

Cyclic 1.0 NDS 1.6 NDS 2.0 NDS 1.0 NDS 1.6 NDS 2.0 NDS 1.0 NDS 1.6 NDS 2.0 NDSParameters 30 Cycles 15 Cycles 8 Cycles 30 Cycles 15 Cycles 8 Cycles 30 Cycles 15 Cycles 8 CyclesHysteretic Initial 32.3 in.-lbs. 71.7 in.-lbs. 110.1 in.-lbs. 35.5 in.-lbs. 64.6 in.-lbs. 85.8 in.-lbs. 139.8 in.-lbs. 308.8 in.-lbs. 437.1 in.-lbs.Energy (8.3) (13.4) (12.2) (14.8) (12.6) (12.1) (19.1) (15.4) (11.6)

Final: 28.3 in.-lbs. 67.4 in.-lbs. 107.8 in.-lbs. 31.3 in.-lbs. 61.2 in.-lbs. 83.8 in.-lbs. 132.9 in.-lbs. 306.8 in.-lbs. 446.5 in.-lbs.(8.9) (15.5) (13.6) (14.3) (12.9) (12.0) (23.6) (13.9) (11.5)

Stiffness Initial 8900 lbs./in. 11700 lbs./in. 13000 lbs./in. 8500 lbs./in. 11800 lbs./in. 13400 lbs./in. 13300 lbs./in. 15700 lbs./in. 16000 lbs./in.(Based on inclusion I (5.2) (5.4) (5.9) (9.1) (9.0) (9.7) (5.5) (7.0) (10.9)of oversize hole) Final: 8400 lbs./in. 11100 lbs./in. 12500 lbs./in. 8200 lbs./in. 11300 lbs./in. 13000 lbs./in. 12100 lbs./in. 14200 lbs./in. 14600 lbs./in.

(6.4) (5.9) (6.5) (9.3) (9.4) (10.3) (5.7) (9.3) (12.2)Stiffness Initial 27400 lbs./in. 27200 lbs./in. 26300 lbs./in. 26200 lbs./in. 28700 lbs./in. 29300 lbs./in. 26200 lbs./in. 24700 lbs./in. 22800 lbs./in.(Based on exclusion (12.2) (12.3) (12.0) (25.3) (23.6) (23.5) (9.5) (10.9) (15.1)of oversize hole) Final: 23000 lbs./in. 24000 lbs./in. 24300 lbs./in. 22800 lbs./in. 26000 lbs./in. 27600 lbs./in. 21800 lbs./in. 21100 lbs./in. 20000 lbs./in.

(14.1) (12.3) (12.5) (25.1) (23.7) (24.0) (9.9) (13.4) (16.4)Damping Initial 6.7 % 8.1 % 8.8 % 7.5 % 7.5 % 7.4 % 10.3 % 10.4 % 9.6 %Ratio (8.1) (14.2) (14.7) (17.7) (11.6) (10.2) (18.5) (15.7) (11.9)(Based on inclusion Final: 5.6 % 7.1 % 8.2 % 6.2 % 6.8 % 7.0 % 8.8 % 9.2 % 8.9 %of oversize hole) (9.4) (17.7) (17.2) (15.3) (12.7) (11.1) (24.8) (15.0) (13.4)Damping Initial 20.8 % 19.0 % 17.8 % 23.0 % 18.1 % 16.1 % 20.3 % 16.4 % 13.7 %Ratio (11.4) (17.0) (19.0) (29.5) (18.0) (16.9) (18.0) (16.7) (13.6)(Based on exclusion Final: 15.3 % 15.5 % 16.0 % 17.1 % 15.4 % 14.7 % 15.9 % 13.6 % 12.3 %of oversize hole) (14.7) (21.3) (22.0) (24.3) (19.6) (18.5) (25.8) (16.7) (15.4)


connections constructed according to the tolerances in the 1991 NDS and 1989 Manual of SteelConstruction. Hysteretic damping values are not affected by the two methods of calculating theproperties due to the amount of energy dissipated being a function of actual construction and simplyplacing constraints on calculations after the tests are complete does not change actual performance.These calculations are simply provided as estimates of the range of possible values for the properties.

Unlike nailed connections a consistant decrease in hysteretic energy dissipation was observedwith cycling of bolted connections between initial and final cycles at each load level. With successivecycling, the displacement at which loading began, increased at a declining rate. An example of thisis shown in Figure 6. In effect, there was a "pinching" or narrowing of the bolted connectionhysteresis with successive cycling, thereby reducing the area inside. The percent decrease was greaterat the lower load levels.

Figure 6: Typical load-displacement time history for a load-controlled cyclic test of a bolt connection.

Cyclic stiffness, as defined in the Property Definitions section, decreased from the initial tofinal cycles due to the incremental increase in displacements at maximum and minimum load for eachcycle. As shown in Figure 6, this increase in displacement occurred at a decreasing rate. Therefore,cyclic stiffness of bolted connections, like that of nailed connections, decreased at a decreasing rate.The percent decrease between initial and final cycles remained fairly constant for a given load level,regardless of whether the effects of over-sized bolt holes were included or not. If the values of cyclicstiffness are compared for when the effects of the over-sized bolt holes are included and when theyare excluded, it becomes evident that the over-sized holes reduce the effective stiffness of theconnections. Connections with tightly fitting bolt holes will be significantly stiffer than connectionwith loose fitting bolts.


Equivalent viscous damping decreased from the initial to final cycles at all load levels for allbolted connections. This was due to the decrease in hysteretic damping with cycling due tonarrowing of the hysteresis, and an increase in potential energy associated with increases indisplacement at maximum and minimum load with successive cycling. Using Equation 1, these twofactors combined to result in a lower equivalent viscous damping ratio for the final cycle. In thenailed connections, the increase in hysteretic damping was always greater than the increase inpotential energy. The opposite was true for the bolted connections, due to the oversize bolt hole.The decrease in equivalent viscous damping ratio was less at higher load levels because the changein hysteretic energy with cycling was less at the higher load levels. These changes are insignificantfrom a practical point when the effects of oversized bolt holes are included, but become significantwhen the effects of the oversized bolt holes are excluded. This indicates that while tight fitting boltswill increase the effective damping of the connections, the magnitude will decrease significantly asthe connection is cycled. However, the lowest average value of equivalent viscous dampingcalculated for connections excluding the effects of the oversized bolt holes was 12.3%. This amountof damping is still significant, and provides an excellent source of structural damping for woodbuildings.

CONCLUSIONS

Results of monotonic and load-controlled cyclic tests of nail and bolt connections have beenpresented. Results show that there is no significant effect of prior cyclic loading on capacity orductility of nail and bolt connections when prior cyclic load levels as high as 2.0 times the 1991 NDSnominal design load. This indicates that design seismic events will not significantly lower theconnection’s ability to resist the loads.

Nail connection capacities showed no statistical change due to prior cyclic loading. Thecapacities of nail connections without prior cyclic loading resulted in factors-of-safety of 2.7 - 5.1 fornormal duration loads and 1.7 - 3.2 for seismic and wind loads. Connections that were loadedcyclicly prior to being tested monotonically had factors-of-safety of 2.9 - 4.4 for normal durationloads and 1.8 - 2.7 for seismic and wind loads. High ductilities associated with nail connections andtheir ability to dissipate large amounts of energy indicate that a factor-of-safety of 1.7 is sufficient toguarantee acceptable performance.

With the exception of light-gauge steel-to-wood connections, prior cyclic loading did notaffect the value of displacement at capacity. Light-gauge steel-to-wood connections experienced aslight increase in displacement at capacity due to local yielding of the steel plate, but the magnitudewas not of practical significance. Ductility of the connections loaded monotonically with no priorloading ranged from 14.3 for light-gauge steel-to-wood connections to 38.2 for plywood-to-woodconnections. These results indicate that ductility of nailed connections is not adversely affected byprior cyclic loading, and ductility is slightly improved for light-gauge steel-to-wood connections.

Pilot holes increased the initial stiffness and yield load of nail connections when compared toconnections fabricated without pilot holes. However, the nail connections without pilot holes hadhigher average ultimate capacity and ductility that nail connections with pilot holes. These effectscan be attributed to the reduced localized spreading of wood fibers surrounding the nail.


Test results indicate that prior cyclic loading, as high as 2.0 times the 1991 NDS nominaldesign values had no adverse effect on capacities of bolted connections for yield modes II, III , III ,S M

and IV. Capacities for monotonic tests with no prior loading resulted in factors-of-safety of 3.7 - 6.9for parallel-to-grain orientations and 5.2 - 13.0 for perpendicular-to-grain orientations whencompared to the 1991 NDS nominal design values for normal duration loads. The same test resultsprovide factors-of-safety for seismic and wind loads of 2.3 - 4.1 for the parallel-to-grain orientationsand 3.3 - 8.1 for the perpendicular-to-grain orientations. Post-cyclic test capacities resulted infactors-of-safety of 3.7 - 7.4 for normal duration loads and 2.3 - 4.6 for seismic and wind loads.Post-cyclic connections were oriented in the parallel-to-grain direction. These factors-of-safetyassociated with bolt capacities are sufficient to provide acceptable performance of wood connections.

Ductilities of bolted connections ranged from 5.4 to 7.5. Comparisons of monotonic capacityfor the connections tested with and without prior cyclic loading indicated that prior load history didnot adversely effect ductility of the connections. The only connection that showed a statisticaldifference in the displacement property was the 4x4-to-4x4 connection. Results showed thatdisplacement at capacity increased slightly, and would indicate that ductility of the connectionincreased slightly due to prior cyclic loading.

Several additional properties were presented to completely describe the monotonic and cyclicperformance of nail and bolt connections. Results presented quantify several cyclic properties suchas hysteretic damping, cyclic stiffness, and equivalent viscous damping. Values of these cyclicproperties illustrate the ability of wood connections to dissipate significant quantities of energy duringcyclic or dynamic loadings expected during natural hazard events such as earthquakes. The abilityto dissipate energy improves a structure’s performance and reliability.

ReferencesManual of Steel Construction., 1989. American Institute of Steel Construction, Inc. (AISC), NewYork, NY.

American Society for Testing and Materials (ASTM), 1989. "ASTM A-36/A-36m-88c, Standardspecification for structural steel." Annual Book of ASTM Standards, Vol 01.06, pp. 106-108.ASTM, Philadelphia, PA.

American Society for Testing and Materials (ASTM), 1992. "ASTM A-446/A-446M-89, Standardspecification for steel sheet, zinc-coated (galvanized) by the hot-dip process, structural (physical)quality." Annual Book of ASTM Standards, Vol 01.09, pp. 37-78. ASTM, Philadelphia, PA.

American Society for Testing and Materials (ASTM), 1990. "ASTM D-143-83, Methods of TestingSmall Clear Specimens of Timber." Annual Book of ASTM Standards, Vol. 04.09. ASTM,Philadelphia, PA.

Dolan, J.D. and S.T. Gutshall, 1994. Detailed Data for Monotonic and Load-Controlled CyclicTests of Nail and Bolt Connections. Virginia Polytechnic Institute and State University, TimberEngineering Report No. TE-1994-002.


Dolan, J.D., S.T. Gutshall, and T.E. McLain, 1994. Sequential Phased Displacement Tests of Nailand Bolt Connections. Virginia Polytechnic Institute and State University, Timber EngineeringReport No. TE-1994-003.

Dolan, J.D. and S.T. Gutshall, 1994. Detailed Data for Sequential Phased Displacement Tests ofNail and Bolt Connections. Virginia Polytechnic Institute and State University, Timber EngineeringReport No. TE-1994-004.

Loferski, J.R. and T.E. McLain, 1991. "Static and Impact Flexural Properties of Common WireNails." ASTM Journal of Testing and Evaluation, 19(4):297-304.

National Design Specification for Wood Construction, 1991. National Forest Products Association.,Washington, D.C.

Documents

Monotonic and Cyclic Tests to Determine Short-Term Load